C. S. Lewis does a fine job in his book Mere Christianity. He talks about the conscience, where does it come from? It seems to hold us all to higher standard, including ourselves, but we fail to fulfill it. It's not just a matter of disliking another's actions because they are inconvenient. For example, say someone takes my shirt, and now I'm mad because I'm missing a shirt. Someone might argue that that is all conscience is. But it's not like that. It's a sense that it was objectively wrong, and so it would be wrong for me to take your shirt even though it improves my situation.

I also recommend his book The Problem of Pain, which talks about man's long history of belief in the supernatural, despite the outlandishness of the idea.

C. S. Lewis was an atheist until his early 30s. He taught at Oxford and then Cambridge, during the first half of the 20th century.